Open Theses & Dissertations

Permanent URI for this collection

https://unbscholar.lib.unb.ca/handle/1882/12778

Browse

Browsing Open Theses & Dissertations by Author "A. Simoneau"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    A study of chip formation, surface defects, and burr formation in orthogonal machining of A356 cast aluminum
    (University of New Brunswick, 2012) Cowperthwaite, Bradley J.; A. Simoneau
    Cast A356 aluminum is commonly employed in the automotive industry due to its high strength to weight ratio and high resistance to corrosion. This relatively inexpensive raw material contains a high silicon content which plays a key role in the machining performance. To understand how the material microstructure is linked to chip formation and surface defects, a series of orthogonal turning tests were performed on A356-F and A356-T6. Experimental findings demonstrated that the chip formation mechanism and resulting surface quality are directly related to the material microstructure. The stronger, more homogeneous structure with hard, silicon phase spheroids allow A356-T6 to produce more uniform chips and a superior surface finish. To examine the tool exit conditions and the burr formation mechanism, a series of orthogonal grooving tests were performed using an orthogonal machining quick-stop on samples of A356-F, A356-T5, and A356-T6. For all tests, a negative burr, or break out, was observed. The mechanism of break out was consistent for all materials but the influence of the material microstructure was found to alter its geometry. Three different exit angles, relative to the cutting direction were tested; 90°, 60°, and 30°. When exiting the workpiece at a 90° angle, a moment was found to act on the chip root eventually causing tensile failure along a break out plane and a uniform chip foot. Exiting at any other angle resulted in a second moment acting upon the chip root, producing a stepped break out.
  • Thumbnail Image
    Item
    Using manganese-sulfide inclusions for localized strain measurements in machining 1144 steel
    (University of New Brunswick, 2012) Watson, Kyle; A. Simoneau
    The following research compares and discusses the results of two series of orthogonal cutting tests of AISI 1045 and AISI 1144 steel, two common alloys in both industry and academia. The focus of these tests was on cutting forces, shear angles and the strains associated with metal cutting. The cutting tests were performed on a CNC lathe to compare the two materials and a quick-stop device in order to study the resulting chip-roots. A custome built quick-stop device was developed in order to study zones of deformation in metal cutting which was based on a equal channel angular press. The device had the benefits of quick set-up times between cutting tests, utilized small samples and was a true representation of orthogonal cutting. In order to validate the resulting cutting speeds and forces, the device was mounted to a force dynamometer. The novel design of this device was able to produce a stopping distance of 2.2 μm or a stopping time of 0.83 μs, an order of magnitude smaller than any experimental work published. The microstructure of 1144 steel lends itself to the study of localized strains in metal cutting. By monitoring the size and shape of the manganese-sulfide inclusions, localized strains were calculated and found to have an average value of 6, with strains as high as 10. Comparably, the general strain calculations based on continuous chip formation produce an average strain of 2.5. From the findings, metal cutting cannot be assumed as a bulk deformation process.